Support for asynchronous adaptation to uplink and downlink traffic demands for wireless communication

ABSTRACT

Technology is discussed to allow transmission points within a Wireless Wide Area Network (WWAN) to adapt to Up Link (UL) and Down Link (DL) traffic demands independently. To mitigate potential interference arising from transmission points scheduled for conflicting UL and DL transmissions, measurements between transmission points can be made to indicate a level of coupling. Based on the various levels of coupling between transmission points, clusters can be formed. Where a high level of coupling is present, transmission points can be included in a common cluster. Where a low level of coupling is present, they can be isolated. Transmission points within the same cluster are scheduled with a common pattern of UL and DL transmissions to avoid interference. Transmission points in different clusters can have different patterns of UL and DL transmission to independently adapt to the relative demands for UL and DL transmissions experienced within these different clusters.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/592,598 filed Aug. 23, 2012 (attorney docket no. P45358) which claimsthe benefit of U.S. Provisional Patent Application Ser. No. 61/612,188,filed Mar. 16, 2012 (attorney docket no. P44413Z) both of which arehereby incorporated by reference in their entirety.

BACKGROUND

Many Wireless Wide Area Networks (WWAN) employ some form of TimeDivision Duplexing (TDD) to schedule both Down Link (DL) and Up Link(UL) traffic. In a TDD environment, DL and UL communications occurbetween a cellular radio tower (tower) and wireless mobile deviceswithin a geographic area covered by the tower that is referred to as acell. DL communications from the tower to the wireless mobile devicesoccur during a first set of timeslots. Conversely, UL communicationsfrom the wireless mobile devices to the tower occur during a second,non-overlapping set of timeslots. The collection of timeslots for whicha tower schedules radio resources for UL and DL communications describesthe UL-DL configuration, or TDD configuration, for the tower and itscorresponding cell.

Unfortunately, when differing, or asynchronous, UL-DL/TDD configurationsare adopted at different transmission points within a WWAN, interferencecan become a problem. The DL transmission of one tower can interferewith the UL reception at another tower. Similarly, the UL transmissionsof one wireless device can interfere with the DL reception at anotherwireless device. To avoid such interference, entire WWANs can operatesynchronously, with a common UL-DL/TDD configuration.

BRIEF DESCRIPTION OF THE DRAWINGS

Features and advantages of the invention will be apparent from thedetailed description which follows, taken in conjunction with theaccompanying drawings, which together illustrate, by way of example,features of the invention; and, wherein:

FIG. 1 is a block diagram illustrating a Wireless Wide Area Networks(WWAN) of evolved Node B (eNodeB) transmission points in anEvolved-Universal Terrestrial Radio Access (E-UTRAN) having coveragecells with asymmetric directional traffic in accordance with an example;

FIG. 2 is a block diagram illustrating two types of interference thatcan occur between cells with asynchronous Up Link (UL)-Down Link(DL)/Time Division Duplexing (TDD) configurations in accordance with anexample;

FIG. 3a is a chart depicting the Cumulative Distribution Function (CDF)of Signal to Interference and Noise Ratios (SINR) for DL reception at aUE for various levels of asynchronous transmission in accordance with anexample;

FIG. 3b is a chart depicting the CDF of SINR for UL reception at aneNodeB for various levels of asynchronous transmission in accordancewith an example;

FIG. 4 is a block diagram illustrating the different levels of couplinginterference that can result from asynchronous transmission depending onthe pair of cells involved in asynchronous transmission based onasynchronous UL-DL/TDD configurations in accordance with an example;

FIG. 5 is a block diagram illustrating the formation of differentclusters of eNodeBs to reflect the different interference impacts thatcan result between different eNodeBs engaged in asynchronoustransmission based on asynchronous UL-DL/TDD configurations inaccordance with an example;

FIG. 6 is a block diagram illustrating the formation of a sub-clusterand the merging of different clusters of eNodeBs to reflect thedifferent interference impacts that can result between different eNodeBsengaged in asynchronous transmission in accordance with an example;

FIG. 7 is a flowchart depicting a process for cluster formation, merger,and eNodeB isolation to accommodate adaptive, asynchronous directionaltransmissions within a WWAN in accordance with another example;

FIG. 8 is a chart depicting the CDF of SINR for UL reception at aneNodeB for various cluster interference levels with two additionalgraphs depicting the CDF for cluster sizes for cluster interferencelevels of −60 dB and −90 dB, in accordance with an example;

FIG. 9 is a pair of charts depicting the CDFs for DL and UL packetthroughput for various cluster interference levels in accordance with anexample;

FIG. 10 is a flowchart depicting a clustering process to accommodateadaptive, asynchronous directional transmissions within a WWAN inaccordance with an example;

FIG. 11 is a block diagram illustrating a device operating at an eNodeBto perform measurement and other functions to form clusters allowingadaptive, asynchronous directional transmissions within a WWAN inaccordance with an example;

FIG. 12 is a flowchart depicting another generalized process formeasuring interference potential to create eNodeB clusters allowingadaptive, asynchronous directional transmissions within a WWAN inaccordance with an example;

FIG. 13 is a block diagram illustrating a device for avoidinginterference while adapting to asynchronous directional traffic atvarious eNodeBs in a WWN in accordance with an example; and,

FIG. 14 is a block diagram of a UE in accordance with an example.

Reference will now be made to the exemplary embodiments illustrated, andspecific language will be used herein to describe the same. It willnevertheless be understood that no limitation of the scope of theinvention is thereby intended.

DETAILED DESCRIPTION

Before the present invention is disclosed and described, it is to beunderstood that this invention is not limited to the particularstructures, process steps, or materials disclosed herein, but isextended to equivalents thereof as would be recognized by thoseordinarily skilled in the relevant arts. It should also be understoodthat terminology employed herein is used for the purpose of describingparticular embodiments only and is not intended to be limiting.

DEFINITIONS

Different terminology for wireless devices is used in differentspecifications. As used herein, a wireless device is a device configuredto wirelessly communicate with a cellular radio tower. Examples ofwireless devices include, but are not limited to a User Equipment (UE)and a Mobile Station (MS). Throughout this application, the term UE canbe used interchangeably with the term MS, or another form of wirelessdevice.

As used herein a transmission point is a wireless communication devicein a Wireless Wide Area Network (WWAN) configured to communicate with aplurality of wireless devices located within a geographic regionreferred to as a cell. Different terminology for transmission points isused in different wireless specifications. Terminology used fordifferent variations of a transmission point can include, but is notlimited to, a Base Station (BS) and an evolved Node B (eNodeB or eNB).The terms are used interchangeably, unless otherwise noted. The actualdefinition of a BS or eNodeB is provided in the respectivespecifications, namely, Institute of Electrical and ElectronicsEngineers (IEEE) 802.16 and Third Generation Partnership Project (3GPP)Long Term Evolution (LTE) specifications.

As used herein, the term “substantially” refers to the complete ornearly complete extent or degree of an action, characteristic, property,state, structure, item, or result. For example, an object that is“substantially” enclosed would mean that the object is either completelyenclosed or nearly completely enclosed. The exact allowable degree ofdeviation from absolute completeness may in some cases depend on thespecific context. However, generally speaking the nearness of completionwill be so as to have the same overall result as if absolute and totalcompletion were obtained. The use of “substantially” is equallyapplicable when used in a negative connotation to refer to the completeor near complete lack of an action, characteristic, property, state,structure, item, or result.

As used herein, the term ‘adjacent’ can mean abutting, but can also meansufficiently near that the interference between adjacent elements is asignificant concern, regardless of any intervening elements.

Other terms may be defined elsewhere in the body of this specification.

EXAMPLE EMBODIMENTS

With respect to such clustering approaches, an initial overview oftechnology embodiments is provided below and then specific technologyembodiments are described in further detail later. This initial summaryis intended to aid readers in understanding the technology more quicklybut is not intended to identify key features or essential features ofthe technology nor is it intended to limit the scope of the claimedsubject matter.

Within a Wireless Wide Area Network (WWAN) employing a form of TimeDivision Duplexing (TDD), many different possibilities exist for Up Link(UL)-Down Link (DL)/TDD configurations, with differing relative numbersof timeslots (resources) for UL and for DL transmission. These differentcombinations of UL and DL dedicated timeslots can allow a transmissionpoint to adapt to different demands for traffic in a given cell. Forexample, where traffic within a cell creates a much greater demand forDL transmission, more DL timeslots can be scheduled for DL transmission.

However, a WWAN comprises a network that can include multipletransmission points, each covering a corresponding geographic regionreferred to as a cell. As is often the case, the demand for DLtransmission time relative to the demand for UL transmission time, andvice versa, can vary, sometimes greatly, from cell to cell. Studiessuggest that the ability to dynamically adapt to DL/UL traffic demandsfrom cell to cell could improve the efficiencies of WWANs, greatlyimproving data throughput. Cells would not be locked into timeslots fordirectional traffic. Instead, one cell could have an UL-DL/TDDconfiguration different from its neighbor, allowing it to adapt to itsown directional traffic needs. Yet, a common UL-DL/TDD configuration iscurrently applied across WWANs to avoid potential interference fromadjacent transmission points scheduled for differing UL and DLtransmission directions.

Although the WWANs can currently adapt to relative DL and UL trafficdemands to form a homogeneous network, with each transmission pointhaving the same TDD configuration, the superior efficiencies of adaptingto such demands on a transmission point level can be difficult, due tothe ensuing interference that can be caused by the differingconfigurations. However, heterogeneous deployments, where low powertransmission points representing small cells operate at the same ordifferent carrier frequencies relative to high power transmissionpoints, have opened possibilities to adapt UL-DL configurations in smallcells due to much higher isolation between those cells.

Differing directional traffic does not have the same impact between alltransmission points. To determine the impact, measurements of potentialinterference, or coupling, between pairs of transmission points can bemade. Where a high potential for interference is measured between a pairof transmission points, the pair of transmission points can be coupledin a common cluster. Where adjacent clusters share one or more commontransmission points, they can also be merged into a common cluster. Thecommon cluster can apply a common UL-DL/TDD configuration to avoid anypotential interference between the transmission points in the commoncluster.

However, where a low potential for interference exists for transmissionpoints in a WWAN, the transmission points can be isolated in differentclusters. At times, transmission points can be isolated as the singleelement in the cluster to which they belong. Since the potential forinterference is low, different clusters can have different UL-DL/TDDconfigurations. As a result, UL-DL/TDD configurations can be assignedwith a much improved level of granularity, paving the way fortransmission points to independently adapt to changing directionaltraffic demands and for large improvements in the efficiency. Additionaldetails are discussed below.

FIG. 1 illustrates a network of evolved Node B (eNodeB) transmissionpoints in a Wireless Wide Area Network (WWAN) 100, which can be anEvolved-Universal Terrestrial Radio Access (E-UTRAN), having coveragecells with asymmetric directional traffic demands, or non-uniform cellloading. The WWAN comprises multiple different cells 102-108. Each cellis comprised of a geographic region over which the respective eNodeB 110a-110 d is configured to communicate with wireless mobile devices 112a-112 d. As an important statement of the generality of embodimentsdiscussed in this disclosure, while the terminology of the 3GPP LTEstandard is often used throughout this specification, it is not intendedto be limiting, and there are exceptions in the use of more generalterminology in portions of this specification to further communicatethis point.

The eNodeBs 110 a-110 d of the various cells 102-108 are configured tosupport both Up Link (UL) and Down Link (DL) transmissions from and toone or more units of User Equipment (UE) 112 a-112 d within the variouscorresponding cells. To accommodate UL and DL transmissions, the WWAN100 uses Time Division Duplexing (TDD) to separate transmissions fromthe eNodeBs to UEs, referred to as DL transmissions, and transmissionsfrom the UEs to the eNodeBs, referred to as UL transmissions. TDD can beused to assign UL and DL transmissions to different timeslots. Byassigning UL and DL transmissions to different timeslots, interferencebetween the transmissions with differing directional traffic can beavoided. For instance, the interference may be caused by a relativelyhigh power signal from a DL transmission that interferes with a lowerpower signal from an UL transmission (i.e. that has an oppositedirection from the DL transmission within substantially the same timeperiod).

Each cell 102-108 contains a number of arrows to and from various UEs112 a-112 d located within each cell. The thin, dashed arrows pointingtoward the eNodeBs 110 a-110 d represent an average amount of time spentin UL transmission for a given time. Similarly, the thick, solid arrowspointing away from the eNodeBs to the UEs represent an average amount oftime spent in DL transmission for the given time. Therefore, therelative number of UL arrows to DL arrows depicts the relative amount ofdirectional traffic demands, in terms of DL and UL transmissions, thateach cell 102-108 experiences over the given amount of time.

Two of the cells depicted 102, 108 experience a markedly greater load ofDL traffic relative to the two other cells depicted 104, 106. Over agiven amount of time, each cell can experience different amounts of DLand UL directional traffic. Therefore, efficient use of temporalresources would dictate the use by each cell of a different amount oftimeslots dedicated to UL transmissions and to DL transmissions.Throughout this application, the allocation of different numbers oftimeslots to DL and UL directional traffic for a given amount of time isdefined as an UL-DL configuration and/or a TDD configuration.

FIG. 2 depicts two types of interference that can occur between cellswith asynchronous UL-DL/TDD configurations. Within the figure, awireless communication environment 200 is illustrated with a firsteNodeB 202 and a second eNodeB 204 is shown. Although the first eNodeBand the second eNodeB are depicted as MaCro-Node (MCN) eNodeBs,depending on the embodiment, either the first eNodeB, the second eNodeB,or both can also be a Low Power Node (LPN). An LPN can comprise one ofone of a micro cell, a pico cell, a femto cell, a home eNodeB cell(HeNB), a Remote Radio Head (RRH), a Remote Radio Equipment (RRE), arepeater, or another type of transmission point having a lower powerthan is typically used at a MCN. In this example, the first eNodeB 202transmits a DL transmission 206 to a first UE 208 associated with thefirst eNodeB. The second eNodeB, however, is scheduled to receive an ULtransmission 210 from a second UE 212 associated with the second eNodeB.

The direction of transmission between the first eNodeB 202 may differfrom that of the second eNodeB 204 because the direction of transmissionat the two eNodeBs is determined by different UL-DL/TDD configurations216, 218. The direction of transmission for timeslots at the firsteNodeB is determined by a first UL-DL/TDD configuration 216, whereas thedirection of transmission for timeslots at the second eNodeB 218 isdetermined by a second UL-DL/TDD configuration.

The first and second UL-DL/TDD configurations 216, 218 are divided upinto 10 different sub-frames (0-9). As used herein, a sub-framecorresponds to an amount of time, i.e., a time slot, for which atransmission point, such as an eNodeB, is scheduled for a singledirection of traffic, whether UL or DL. In FIG. 2, at the fifthsub-frame (labeled sub-frame 4), the first eNodeB 202 is scheduled fordownlink transmission according to the first UL-DL/TDD configuration216. This is in conflict with the scheduling for UL reception at thefifth sub-frame (labeled sub-frame 4), according to the second UL-DL/TDDconfiguration 218 of the second eNodeB 204. The conflict in thedirection of transmission between the two eNodeBs sets the stage for twotypes of interference.

A first type of interference 220 is depicted with a large ‘X’ where thebold, solid arrow representing the DL transmission 206 from the firsteNodeB 202 crosses the thin, dashed arrow representing the ULtransmission 210 from the second UE 212 associated with the secondeNodeB 204. (The UL transmission is also represented by the curved wavelines emanating from the second UE.) In this first type of interference,the DL transmission from the first eNodeB interferers with ULtransmissions that the second eNodeB is scheduled to receive.

Since, the DL transmission 206 from the first eNodeB 202 interferes withthe UL reception at the second eNodeB 204, this first type ofinterference 220 is referred to herein astransmission-point-to-transmission-point interference and/oreNodeB-to-eNodeB interference. Due to the power levels at which eNodeBscommonly transmit DL transmissions, this first type of interference canbe the most problematic, as indicated by the large size of the ‘X, inFIG. 2. Indeed, the received power of the useful signal from the secondUE 212 can often be lower than the power of the interference from the DLtransmission. This can make it difficult or impossible for the ULtransmission to be received at the second eNodeB.

A second type of interference 222 is also depicted in FIG. 2 with asmaller ‘X’ where the curved wave lines emanating from the second UE 212associated with UL transmission 210 from the second eNodeB 204 cross thebold, solid arrow representing the DL transmission 206 from the firsteNodeB 202. (The UL transmission is also represented by the thin, dashedarrow.) This second type of interference arises from the interferencecaused by the UL transmission from the second UE with the DLtransmission from the first eNodeB 202 as it is received by the first UE208 associated with the first eNodeB.

Since, the UL transmission 210 from the second UE 212 interferes withthe reception at the first UE 208 of the DL transmission 206 from thefirst eNodeB 202, this second type of interference is referred to hereinas wireless-mobile-device-to-wireless-mobile-device interference and/orUE-to-UE interference. Since UEs commonly transmit at lower powers thaneNodeBs, due to UL power control that compensates for pathlosspropagation, in certain scenarios UE-to-UE interference can arise wherea UE engaged in UL transmission, corresponding to the second UE in FIG.2, is sufficiently close to a DL receiving UE, corresponding to thefirst UE in FIG. 2. Depending on the embodiment, such distances may bemeasured in tens to hundreds of meters. Therefore, UE-to-UE interferenceis depicted with a smaller ‘X.’

The conflicts between transmission directions arising from the use ofthe first UL-DL/TDD configuration 216 and the second UL-DL/TDDconfiguration 218 by two adjacent eNodeBs 202, 204 provide only someexamples of instances where such conflicts can arise. Several otherexamples can be demonstrated from the table 224 of possible UL-DL/TDDconfigurations depicted in FIG. 2. The possibilities arising from thetable are not intended to be limiting. A number of different UL-DL/TDDconfigurations may, or may not, be used that are not depicted in thetable, depending on network configuration, network usage load, and otherfeatures, as can be appreciated. The table merely depicts UL-DL/TDDconfigurations specified for Release 9 of the Third GenerationPartnership Project (3GPP) Long Term Evolution (LTE) standards. However,other approaches to UL-DL/TDD configurations are possible.

In the table 224, each configuration of the seven UL-DL/TDDconfigurations occupies a frame, which corresponds to 10 ms oftransmission time. After the time required for frame transmissionelapses, a chosen UL-DL/TDD configuration can be repeated, or a new onechosen. Each frame can comprise ten, 1 ms sub-frames. Each sub-frame cancorrespond to a timeslot.

Accordingly, each sub-frame can be allocated for either UL transmission,indicated in FIG. 2 with a ‘U,’ or DL transmission, indicated by a ‘D.’Certain sub-frames can also be allocated for special transmissionperiods, indicated by an ‘S,’ such as those for Downlink Pilot Timeslot(DwPTS), Guard Period (GP), and Uplink Pilot Timeslot UpPTStransmissions. As can be appreciated, each UL-DL/TDD configurationcorresponds to a different pattern of DL and UL transmission allocationswith differing amounts of allocations for UL transmissions relative toDL transmissions. These differing patterns lead to the potential forinterference between adjacent cells with eNodeBs with differing TDDconfigurations.

FIG. 3a provides a chart 300 with the Cumulative Distribution Functions(CDF) of Signal to Interference and Noise Ratios (SINR) for DL receptionat a UE where UE-to-UE interference is an issue. The CDFs provideresults from a study performed by the 3GPP reported in R4-120837, “DL-ULinterference analysis for single operator macro-outdoor pico deploymentscenario in adjacent channel,” INTEL CORP., February 2012. The CDFsresult from simulations of different levels of conflicting transmissiondirections in a network with LPNs comprising pico cells.

The simulations involve four LPNs that are randomly distributed apartfrom one another. The CDF corresponding to the solid curve reports thecase where all pico cells are engaged in DL transmission. The dottedcurve corresponds to the CDF where half of the pico cells are engaged inUL transmission and half are engaged in DL transmission. The CDFcorresponding to the dashed curve reports the case where half of thepico cells are engaged in DL transmission and half are turned off.Conversely, the CDF corresponding to the mixed, dashed-and-dotted curvereports the case where half of the pico cells are engaged in ULtransmission and half are turned off.

In the FIG. 3a , SINR is measured at a UE that receives DL transmissionfrom the LPN. Where all the LPNs are also engaged in DL transmission(solid curve), the DL transmissions from the LPNs interfere at the UEside. Therefore, the CDF for this scenario represents the lowest SINRs.

The SINR of the CDF, however, stays low even when half of the LPNs areswitched from DL transmission to UL transmission (dotted line). Thecontribution of UE-to-UE interference can be seen when the scenario with50% DL LPN transmission and 50% UL LPN transmission (dotted curve) iscompared to the scenario with 50% DL LPN transmission and 50% of theLPNs turned off (dashed curve), for which SINR values in thecorresponding CDF are slightly higher. The final CDF, for the scenario,with 50% UL LPN transmission and 50% of the LPNs turned off (mixed,dashed-and-dotted curve), corresponds to the highest values for SINR.

FIG. 3b provides CDFs 302 of SINR for UL reception at an eNodeB whereeNodeB-to-eNode interference is an issue. The CDFs report results forthe study performed by the 3GPP reported in R4-120837, as discussedabove. As in FIG. 3a , reports of various CDFs with respect to SINR,measured in dB, are provided according to different levels ofconflicting transmission directions in a network with LPNs comprisingpico cells. As was also the case in FIG. 3a , four LPNs are randomlydistributed apart from one another within the coverage area of an MCNeNodeB.

The CDF corresponding to the solid, bold curve reports the case wherehalf of the pico cells are engaged in UL transmission and half areengaged in DL transmission. The dashed curve corresponds to the CDFwhere half of the pico cells are engaged in DL transmission and half areturned off. The CDF corresponding to the solid, plain curve reports thecase where all pico cells are engaged in UL transmission. The dottedcurve represents the CDF for the case where half of the pico cells areengaged in UL transmission and half are turned off.

The strong potential impact of eNodeB-to-eNodeB interference can be seenclearly in the various CDFs depicted in FIG. 3a . In the figure, SINR ismeasured at the eNodeB receiving UL transmission from a UE within theMCN's coverage area. A shelf spanning approximately 30 dB, circled bythe dashed ellipse in FIG. 3b , corresponds to eNodeB-to-eNodeBinterference problems for two of the scenarios reported with CDFs. Ascan be appreciate, this eNodeB-to-eNodeB interference 220, as explainedin FIG. 2, can take the power associated with the useful signal belowthe power associated with noise and interference.

The CDFs manifesting eNodeB-to-eNodeB interference both involvescenarios where DL transmissions interfere with the UL transmission. Themost pronounced interference arises in the scenario with 50% of the LPNsengaged in DL transmission and 50% engaged in UL transmission (solid,bold curve). The interference remains strong, albeit slightly reduced,for the scenario with 50% of the LPNs engaged in DL transmission and 50%are turned off (dashed curve), presumably reducing UL-to-ULinterference.

However, much larger improvements in SINR are seen where none of theLPNs are engaged in DL transmission, potentially interfering with ULreception. Where all the LPNs are engaged in UL transmission (solid,plain curve), SINR greatly improves. The SINR is slightly better where50% of the LPNs are engaged in UL transmissions and 50% of the LPNs areoff (dotted line). Again, this additional improvement presumably resultsfrom reducing UL-to-UL interference by removing approximately half ofthe UL transmissions from UEs.

The problems of UE-to-UE and eNode-to-eNodeB interference arising whereadjacent cells have differing transmission directions are significant.Therefore, a common UL-DL/TDD configuration is currently imposed acrosscellular networks to avoid differing transmission directions and thetypes of interference appointed therewith. However, this blanketapproach results in large inefficiencies. This is because the need forUL transmission resources to DL transmission resources often variesgreatly across such a network with respect to geographic region and withrespect to time. If, therefore, interference problems could be mitigatedso that one cell could have an UL-DL/TDD configuration different fromits neighbors, timeslots for transmission directions could be used moreefficiently to adopt to changing directional traffic loads in differentregions of the network.

FIG. 4 illustrates different levels of coupling interference that canresult from asynchronous transmission. As used herein, the term couplinginterference, coupling level, and/or interference level refers to ameasurement of a DL transmission by one eNodeB/transmission point atanother eNodeB/transmission point. The level of coupling interferencethat is measured can be indicative of the potential for eNodeB-to-eNodeBand UE-to-UE interference that differing transmission directions betweenthe two eNodeBs can cause. As used herein, the term asynchronous trafficrefers to differing directional transmission across transmission pointswithin a WWAN 400. As shown in FIG. 4, the differing levels of couplinginterference can be leveraged to improve the efficiency with whichdirectional transmission timeslots are allocated within the WWAN in waysthat allow different transmission points to adapt to differingdirectional traffic needs with respect to time and spatial region.

Three different eNodeBs, or transmission points, 402, 404, and 406, aredepicted in FIG. 4. Although only three eNodeBs are depicted, any numberof eNodeBs can be involved. Also, although the eNodeBs are depicted asLPNs, any combination of LPNs and MCNs are possible. The first eNodeB402 in the example of FIG. 4 has a corresponding cell 408 defined by acoverage area 408 with multiple UEs therein. An example UE 414 islabeled to indicate the appearance of UEs in the figure. Similarly, thesecond eNodeB 404 also has a corresponding cell 410 defined by acoverage area with multiple UEs therein. Likewise, the third eNodeB 406also has a corresponding cell 412 defined by a coverage area withmultiple UEs therein.

As indicated by the solid, bold arrow, a relatively strong level ofcoupling interference 416 exists between the first eNodeB 402 and thesecond eNodeB 404. However, as indicated by the first dashed, thin arrowa relatively weak level of coupling interference 418 exists between thefirst eNodeB 402 and the third eNodeB 406. Additionally, as indicated bythe second thin, dashed arrow, another relatively low level of couplinginterference 420 also exists between the second eNodeB 404 and the thirdeNodeB 406.

To determine the level of coupling interference 416 between itself andthe second eNodeB 404, the first eNodeB 402 can measure a unit ofcoupling information, make a coupling measurement, or determine acoupling level between the first eNodeB and the second eNodeB 404. Themeasurement can be based on DL transmission from the second eNodeB, suchas the measurement of a pathgain from one or more reference signals inthe DL transmission. Cell-specific reference signals, channel stateinformation reference signals, or other signals can be used to measurepathgain. Based on such measurements, transmit power reduction can beapplied between cells in order to reduce coupling and make those cellsmore isolated in the sense that opposite transmission direction does notdeteriorate their performance.

Several other types of measurements are also possible, including, by wayof illustration and without limitation, a measurement of received signalstrength, a Reference Signal Received Power (RSRP) measurement, and aReference Signal Received Quality (RSRQ) measurement. The RSRP and RSRQmeasurements can be defined in one or more of the standards for ThirdGeneration Partnership Project (3GPP) Long Term Evolution (LTE) Release8, Release 9, Release 10 and Release 11. Throughout this application,Release 11 can refer to the prerelease issued by 3GPP LTE in the springof 2012.

Once a unit of coupling information has been measured, a clusteringdetermination can be made based on the measured unit of couplinginformation. Where the measured unit of coupling information indicates ahigh level of coupling interference 416 between the first eNodeB 402 andthe second eNodeB 404, a determination can be made to cluster the firsteNodeB and the second eNodeB for purposes of UL-DL/TDD configuration.Where the coupling information indicates a relatively low level ofcoupling interference, a determination can be made that the first eNodeBand the second eNodeB are sufficiently isolated to have differentUL-DL/TDD configurations in the different clusters to which they below.

A determination on which transmission points can be clustered togetherto reduce undesirable levels of coupling interference and whichtransmission points can maintain a different TDD configuration, due torelatively low levels of coupling interference, can be made on the basisof one or more conditions being met. As an example a first condition canbe that a performance of the first eNodeB is not substantially degradedby a transmission direction of an adjacent eNodeB. A second conditioncan be that a change of the transmission direction of the adjacenteNodeB does not substantially degrade the performance of the firsteNodeB. Other conditions are possible. In some embodiments, substantialdegradation can be identified relative to a selected coupling thresholdlevel value.

A coupling threshold level can be determined by an estimate of a levelof inter-cell interference calculated from the unit of couplinginformation where a transmission power of the adjacent eNodeB is known.In some embodiments, coupling interference can be determined based on anaverage power of a useful UL signal, measured in a time slot when UEsare scheduled for UL transmission to the measuring eNodeB. The clusterthreshold can be determined based on an average level of UL measurementsfrom multiple eNodeBs. Other approaches for selecting a couplingthreshold level are also possible, as can be appreciated.

A determination that the first eNodeB 402 and the second eNodeB 404 canbe isolated due to a relatively low level of coupling interference canresult in configuring the first eNodeB with a first UL-DL/TDDconfiguration independent from a potentially differing UL-DL/TDDconfiguration for the second eNodeB. The ability to assign differingUL-DL/TDD configurations can increases the efficiency with whichtimeslots are scheduled for directional traffic. Conversely, where adetermination has been made to cluster the first eNodeB and the secondeNodeB 404, they can be configured with a common UL-DL/TDDconfiguration. The common UL-DL/TDD configuration can mitigateeNodeB-to-eNodeB and UE-to-UE interference where a measurementindicating a relatively high level of coupling indicates that theseforms of interference could be a problem. Coordination of the commonUL-DL/TDD configuration can occur over a backhaul link 422 between thefirst eNodeB and the second eNodeB. The backhaul link between theeNodeBs may be preexisting or established or modified on the basis ofthe determination. In certain embodiments, the coordination can beachieved over an X2 interface as defined in one or more of the standardsfor 3GPP LTE Release 8, Release 9, Release 10 and Release 11.Alternatively, if one eNodeB controls several cells, it can beimplemented in a vendor-specific protocol.

Similar measurements can be made between additional eNodeBs within theMAN 400, resulting in a number of different clusters, which can haveanywhere from a single transmission point to many transmission pointstherein. Due to the relatively high level of coupling interference 416in the example of FIG. 4, the first eNodeB 402 and the second eNodeB 404are included in a common cluster 424. Both eNodeBs in the common clustercan be configured with a common UL-DL/TDD configuration 426(corresponding to UL-DL/TDD configuration # 3 in the table 224 providedin FIG. 2), for which additional eNodeBs could also be configured ifthey were assigned to the same cluster.

However, the third eNodeB 406 has relatively low coupling interferences418, 420 between the third eNodeB and the first eNodeB 402 and thesecond eNodeB 402. Accordingly, the third eNodeB can be isolated in itsown cluster 228. Since it is isolated in its own cluster, the thirdeNodeB can have a different UL-DL/TDD configuration, such as thedifferent isolated UL-DL/TDD configuration 430 (corresponding toUL-DL/TDD configuration # 4 in the table 224 provided in FIG. 2) for theisolated cluster depicted in FIG. 4.

Due to the differing UL-DL/TDD configurations 426, 430 in FIG. 4, at thefifth timeslot/sub-frame (indicated by number 4), the UEs within thethird coverage area 412 corresponding to the isolated cluster 428 areengaged in UL transmission 432. At the same time, the first eNodeB 402and the second eNodeB 404 within the first coverage area 408 and thesecond coverage area 412 respectively of the common cluster 418 areengaged in DL transmission 434. Hence, the differing directionaltransmission traffic demands within the two clusters can be efficientlyaccommodated with differing UL-DL/TDD configurations without leading tounacceptable eNodeB-to-eNodeB and UE-to-UE interference problems.Additionally, these UL-DL/TDD configurations 426, 430 can be changedindependently in near real time to adapt to changing directional trafficdemands within the two clusters that can be constantly monitored.

FIG. 5 depicts the formation of multiple clusters based on couplinglevels between transmission points. Throughout this application, theterm ‘coupling level’ refers to a measurement of potential interference.Several, non-limiting examples of such measurements have been providedpreviously. Five different LPN eNodeBs 502 a-e with their correspondingcoverage areas 504 a-e are depicted in FIG. 5. However, any number ofeNodeBs and combinations of LPNs and MCNs are possible. Additionally, acoupling level between each pair of eNodeBs is also depicted. Couplinglevels above a coupling threshold are depicted by solid, bold arrows508, 510. Coupling levels that are not above the coupling threshold aredepicted as thin, dashed arrows. The coupling threshold is set at apredetermined level at which the potential for eNodeB-to-eNodeB andUE-to-UE interference can begin to be a problem, with some possibleconsiderations discussed previously.

The two coupling levels above a coupling threshold 508, 510 can be thebasis for forming a first cluster 512 with the first eNodeB 502 a andthe second eNodeB 502 b and a second cluster 514 with the fourth eNodeB502 d and the fifth eNodeB 502 e. Since there is no coupling level abovethe coupling threshold between the third eNodeB 502 c and any othereNodeB, a third cluster 516, with a single eNodeB, can be formed. Eachcluster can have a different UL-DL/TDD configuration, as indicated bythe first UL-DL/TDD configuration 518 (corresponding to UL-DL/TDDconfiguration # 4 in the table 224 provided in FIG. 2) for the firstcluster 512, the second UL-DL/TDD configuration 520 (corresponding toUL-DL/TDD configuration # 3 in the table 224 provided in FIG. 2), forthe second cluster 514, and the third UL-DL/TDD configuration 522(corresponding to UL-DL/TDD configuration # 6 in the table 224 providedin FIG. 2), for the third cluster 516.

The three clusters are depicted at the fifth timeslot/sub-frame (labeled#4), where potential conflicts in directional traffic exist, butinterference problems are mitigated by the formation of differentclusters. Potential conflicts also exist on the eighth and ninthsub-frames (labeled #7 and #8 respectively). As can be appreciated fromthe various arrows between UEs and eNodeBs, the formation of severaldifferent clusters allows the WWAN 500 to adapt in near real time todiffering directional transmission traffic loads within the differentclusters. Differing traffic loads are depicted by differing numbers ofarrows from UEs to eNodeBs and from eNodeBs to UEs depicting differingrelative demands for UL and DL transmissions respectively. An example UE506 is labeled to indicate the appearance of additional UEs in thefigure. As can be appreciated, the various UL-DL/TDD configurations 518,520, and 522 are tailored to meet these demands for UL and DLtransmissions.

To facilitate the determination of UL-DL/TDD configurations 518, 520,and 522, eNodeBs can communicate their directional traffic needs betweenone another over low-latency backhaul infrastructure. Individual eNodeBswithin a cluster can be configured to send traffic direction informationabout traffic direction needs and receive such traffic directioninformation. Decisions about a common UL-DL/TDD configuration or arestricted set of UL-DL configurations for a cluster 512, 514, and 516can be made on the basis of joint UL and DL needs throughout the clusterand/or splitting differences between UL and DL traffic demands atindividual eNodeBs in the cluster.

Decisions about UL-DL/TDD configurations can be made at individualeNodeBs and/or at a network level. Where determinations are made at anetwork level, information used to make such determinations can becommunicated to the network level over an S1 interface, as described inany combination of Release 8, Release 9, Release 10, and Release 11 ofthe 3GPP LTE specifications. Determinations for UL-DL/TDD configurationsfor different clusters can be constantly made and updated independent ofone another to respond to dynamically changing directional traffic loadsmonitored within individual clusters.

FIG. 6 illustrates the merger of clusters to form a larger cluster, withpotential sub-clusters. As before, several different LPN eNodeBs 602a-e, which can represent any number of eNodeBs and combinations of LPNsand MCNs, with their corresponding coverage areas are depicted in FIG.6. Additionally, coupling levels between pairs of eNodeBs are alsodepicted, where solid, bold arrows 604, 606, 608, represent couplinglevels above a coupling threshold and thin, dashed arrows representcoupling levels that are not above the coupling threshold.

Based on the three coupling levels 604, 606, 608 above the couplingthreshold, three clusters can be formed: a first cluster 612 between thefirst eNodeB 602 a and the second eNodeB 602 b; a second cluster 614between the third eNodeB 602 c and the fourth eNodeB 602 d; and, a fifthcluster 616 between the fourth eNodeB 602 d and the fifth eNodeB 602 e.As can be appreciated, however, the second cluster and the third clustershare a common eNodeB, the fourth eNodeB 602 d. Therefore, to avoidpotential eNodeB-to-eNodeB interference, the second and third clusterscan be merged 618.

The action of merging 618 the second cluster 614 and the third cluster616 results in a different prior clustering configuration 600 a beforeaccomplishment of the merger 620 with respect to a post clusteringarrangement 600 b afterward. After accomplishment of the merger, only asmall cluster 612 and a large cluster 622 remain. In certainembodiments, by way of illustration and not limitation, a mergerdetermination can be made in response to an eNodeB list communicatedover backhaul infrastructure, such as an X2 interface and an S1interface, from one or more adjacent clusters. The eNodeB list caninclude a list of eNodeBs within a cluster such that the presence of oneor more common/intersection eNodeBs between clusters can be determined.Where one or more common/intersection eNodeBs are present betweenclusters, a determination to merge clusters can be made. Where there arenot one or more common/intersection eNodeBs present, a determination toleave the clusters unaltered may be made, depending on potentialcoupling threshold level values.

The merger process can also be performed in reverse. Where one or morecommon eNodeBs no longer connects portions of a larger cluster,according to an updated measurement, the larger cluster can be dividedinto smaller clusters. Conversely, where the one or more previouslycommon eNodeBs again become active in ways that justify reconnecting thelarger cluster, the cluster should be reformed.

Additionally, in certain embodiments, a potential for sub-clustering canbe capitalized upon. Although both the third eNodeB 602 c and the fiftheNodeB 602 e share coupling levels 608, 610 above a coupling thresholdwith the fourth eNodeB 602 e, another coupling level 624 between thethird and fifth eNodeBs is below the coupling threshold, as indicated bythe thin, dashed arrow. Since the fourth eNodeB 602 d is still shared incommon, the third and fourth eNodeBs belong to the same cluster 622.However, due to the low coupling level between the third and the fiftheNodeBs, small variations can be appropriate in the configurations ofthe third and fifth eNodeBs for different scenarios.

One such scenario, provided by way of illustration and not limitation,can include a scenario where the forth eNodeB 602 d is scheduled totransmit an Almost Blank Sub-frame (ABS). Other non-limiting scenariosinclude scenarios where the fourth eNodeB is configured to engage inbeam forming and/or power reduction during certain timeslots/sub-frames.During such timeslots and sub-frames the third eNodeB 602 c and thefifth eNodeB 602 e can engage in transmissions with conflictingdirections, because of the relatively low coupling level 624 betweenthem. Therefore, the merged, larger cluster 624 can be divided intosub-clusters, which can have different UL-DL/TDD configurations onsub-frames for scenarios similar to those described above. FIG. 6depicts such sub-clusters in terms of a first sub-cluster 626 for thethird eNodeB and a second sub-cluster 628 for the fourth eNodeB.Although the sub-clusters in FIG. 6 only comprise one eNodeB, multipleeNodeB within a single sub-cluster are also possible.

FIG. 7 provides a flowchart depicting a process 700 for clusterformation consistent with one example. The process comprises measuring710 a unit of coupling information between two transmissionpoints/eNodeBs. The coupling measurement can be made on one eNodeB basedon a portion of a DL transmission from an adjacent eNodeB. The couplinginformation can take any of the forms described above in addition tometrics apparent to those of ordinary skill in the art. A couplingthreshold is then determined 720. In one example provided for purposesof illustration, not limitation, the coupling threshold can bedetermined based on a useful signal power estimate generated frommeasurements of UL transmissions from eNodeBs within the coverage areaof a particular eNodeB. In other embodiments, a coupling threshold valueis received over a backhaul link, or retrieved from memory. However,other approaches are discussed in this specification and will beapparent to those of ordinary skill in the art.

The process 700 continues by making a clustering determination 730. Thestep of making a clustering determination can be broken out into asub-routine 730 involving comparing 732 the unit of coupling informationto the coupling threshold. Within the sub-routine, a decision 734 canthen be made as to whether a coupling metric related to the couplinginformation, such as a pathgain in one non-limiting example, is below acoupling threshold. If the answer is yes, a determination 736 is madethat the measuring eNodeB can be isolated 736 in a different clusterfrom the adjacent eNodeB. Where the answer is no, a determination 738can be made that the pair of eNodeBs can be combined in a commoncluster.

After the isolation decision 734, the clustering determinationsub-routine 730 is complete. The method 700 then continues by carryingout 740 one of the determinations 736, 738, as indicated by thedetermination sub-routine, making that sure the measuring eNodeB and theadjacent eNodeB are in the right cluster or clusters relative to oneanother. The process can then continue for another pair of eNodeBs in aWWAN.

FIG. 8 provides a chart 800 illustrating a tradeoff between improvementsto SINR resulting from clustering and directional traffic adaptationcapabilities. In the chart, the CDFs with respect to SINR, measured indBs, are provided for a study of several different coupling thresholds.These CDFs report SINR for a scenario similar to the one described abovein FIG. 3b , but for which more LPNs, comprising pico cells, aredistributed in the coverage area of a MCN where SINR of UL transmissionsfrom a UE in the coverage area are measured. Also, instead ofdirectional traffic being set at a granularity of individual LPNs,transmission direction is determined for entire clusters.

The chart 800 reports the study results for a scenario where 50% of theLPNs are engaged in UL transmission and 50% of the clusters are engagedin DL transmission. As indicated in the table of threshold values 802,the CDF with respect to SINR is reported for various coupling thresholdsin the table. The coupling threshold can, as discussed above, determinewhether one transmission point can be isolated from another so that itcan independently adapt to the directional traffic needs within itscoverage area.

Where a coupling metric from a measured unit is above the couplingthreshold, eNodeB-to-eNodeB interference, and/or UE-to-UE interferencecan be deemed to be sufficiently great not to allow the pair of eNodeBsfor which the measurement was made to be isolated in different clusterswith different directional traffic. Conversely, where the couplingmetric for a coupling measurement is below the coupling threshold, thepair of eNodeBs can be allowed to adapt independently to the directionaltraffic loads which they experience. Therefore, the determination of thecoupling threshold can involve a tradeoff between traffic adaption,associated with many clusters and small numbers of eNodeBs therein, andavoiding eNodeB-to-eNodeB interference, and/or UR-to-UR interference.This tradeoff is demonstrated in the chart 800 and its accompanyinggraphs 804, 806.

Table 802 indicates that the long-dashed curve reports the CDF withrespect to SINR for the scenario where no clustering is allowed. (Thisscenario is similar to the scenario depicted by the bold, solid curve inFIG. 3b .) The solid, bold cure depicts the results for the highestcoupling threshold value of −60 dB, which refers to a value for ameasured path gain. However, other coupling metrics are possible inalternative embodiments. Results are also reported for couplingthresholds of −70 dB (short-dashed curve), −80 dB (dotted curve), and−90 dB (solid curve), which is the lowest coupling threshold value.

A CDF of cluster size, in terms of eNodeBs in a given cluster, isprovided in a first graph 804 for the highest clustering threshold of−60 dB. A second graph 806 provides the CDF for the lowest clusteringthreshold of −90 dB. A raised clustering threshold allows more eNodeBsto be isolated from one another in more clusters of smaller sizes.Hence, the first graph for the highest clustering threshold reports aCDF with over 90% of clusters including a single eNodeB. Almost eachtransmission point, therefore, would be allowed to independently adaptto the directional traffic demands placed upon it. However, therelatively high value for the coupling threshold, as indicated by thechart 800 does not do much to improve SINR, meaning the eNodeB-to-eNodeBinterference and/or UE-to-UE interference can be problems.

At the other extreme, a coupling threshold of −90 dB prevents moreeNodeB-to-eNodeB interference and/or UE-to-UE interference, placing agreater restriction on transmission points that can have differentdirectional traffic. As a result, chart 800 indicates that SINR isgreatly improved. However, the second graph 806 corresponding to thislow coupling threshold shows that fewer clusters are formed and thoseclusters tend to have more eNodeBs within them. For example, only about65% of transmission points are able to independently adapt todirectional traffic demands, making the network as a whole less capableof adapting to these demands.

As demonstrated by FIG. 8, therefore, the coupling threshold is anoptimization parameter. The optimization parameter can be optimized fora particular WWAN in terms of competing needs to avoid eNodeB-to-eNodeBinterference and/or UE-to-UE interference on one side and to adapt todirectional traffic demands on the other side. In some embodiments suchoptimization can be automated based on feedback. Such feedback caninclude, by way of example and not limitation, feedback aboutthroughput, a pathgain measurement, SINR, directional traffic loading atone or more transmission points, and/or one or more coupling levels.

FIG. 9 provides a pair of charts 902, 904 demonstrating the improvementsin DL and UL throughputs that clustering achieves. The first chart 902provides several CDFs, corresponding to various coupling thresholds,plotted with respect to packet throughput, in Mega bits per second(Mbps), received at a UE during DL transmission from a transmissionpoint. Conversely, the second chart 904 provides several CDFs for thesame coupling thresholds, plotted with respect to packet throughput, inMbps, received at a transmission point from a UE during UL transmission.The various threshold values for the various CDF curves in both chartsare provided in the threshold table 906.

The CDFs plotted in the charts 902, 904 report simulations similar tothose discussed above with respect to FIG. 3 and FIG. 8. The simulationis conducted using File Transfer Protocol (FTP) traffic model parametersdefined in 3GPP R1-120080, where λ_(D)=λ_(U)=1, FTP file size=0.5 MB,and time scales=10 ms. As indicated in the threshold table 906, thesolid curve reports the case where UL-DL/TDD configurations are changedsemi-statically, measured in minutes and hours, across the network inaccordance to existing TDD technologies.

The long-dashed curves depict the results for a coupling threshold of−90 dB, which refers to a value for a measured path gain. However, othercoupling metrics are possible in alternative embodiments. Results arealso reported for coupling thresholds of −80 dB (dotted curve), and −70dB (short-dashed curve). A mixed, dashed-and-dotted curve is provided toindicate what the CDFs for packet throughput would be in a hypotheticalcase if each transmission point could adapt independently to directionaltraffic needs without worrying about interference.

As can be appreciated, the packet throughputs are increased by almost 10Mbps for the DL reception at a UE and by more than 5 Mbps at the ULreception at the transmission point. Therefore, the proposed approachesto interference management can be used to resolve the eNodeB-to-eNodeBinterference and/or UE-to-UE interference problems. Furthermore, theproposed solutions are applicable for different types of deploymentscenarios.

FIG. 10 depicts a flowchart for a particular clustering method 1000 forinterference management in a wireless network with different UL and DLtime timeslots and adaptive, asynchronous directional traffic resourceallocation consistent with an example. The method can, but need notnecessarily, be embedded in a computer program product comprising anon-transitory computer usable medium. The computer readable medium canhave a computer readable program code embodied therein. The computerreadable program code can be adapted to be executed to implementinstructions for the method.

The method comprises measuring 1010, at a first eNodeB, a unit ofcoupling information between the first eNodeB and an adjacent eNodeB.The unit of coupling information is used to make a clusteringdetermination. The clustering determination, as depicted in block 1020,can be a first determination that the first eNodeB and the adjacenteNodeB belong in a common cluster. Conversely, the clusteringdetermination can be a second determination that the first eNodeB andthe adjacent eNodeB are isolated, meaning they can be in differentclusters. Where the first determination has been made, the method 1000further comprises configuring 1030 the first eNodeB and the adjacenteNodeB with a common UL-DL configuration. Where the second determinationhas been made, the method further comprises configuring 1030 the firsteNodeB with a first UL-DL configuration independently from a potentiallydiffering UL-DL configuration pertaining to the adjacent eNodeB.

In certain embodiments, making the clustering determination, based onthe unit of coupling information, further comprises reaching the firstdetermination where at least one of a first condition and a secondcondition is met. The first condition is that a performance of the firsteNodeB is not substantially degraded by a transmission direction of theadjacent eNodeB. The second condition is that a change of thetransmission direction of the adjacent eNodeB does not substantiallydegrade the performance of the first eNodeB. If the right combination ofthese two conditions is not met, the second determination is reached.

In some embodiments, a coupling metric is selected to characterize theunit of coupling information. A coupling threshold is also used todetermine that the performance of the first eNodeB is substantiallydegraded where the unit of coupling information is either at or abovethe coupling threshold for the coupling metric. Otherwise, adetermination is made that the first eNodeB is not substantiallydegraded where the unit of coupling information is below the couplingthreshold for the coupling metric.

Such embodiments can further comprise determining the coupling thresholdbased on one of several different possibilities. One example of such apossibility is an estimate of a level of inter-cell interferencecalculated from the unit of coupling information where a transmissionpower of the adjacent eNodeB is known. Another example is an averagepower of a useful UL signal. Yet another example is an average level ofuplink inter-cell interference where all eNodeBs in the common clusteroperate to receive uplink transmission.

Certain embodiments can comprise merging the common cluster with asecond cluster. The clusters are merged in such embodiments where thecommon cluster and the second cluster have at least one eNodeB incommon. This one or more eNodeBs couple the common and adjacentclusters. Similarly, certain embodiments can comprise dividing a mergedcluster into sub-clusters. This division can take place where one ormore adapted eNodeBs within the merged cluster can adapt to changingtraffic demands in a manner such that the following scenario is met. Thescenario is that the first condition and the second condition, asdiscussed above, no longer obtain between the one or more adaptedeNodeBs and one or more additional eNodeBs in the merged cluster. Whenthis scenario is met, each sub-cluster can apply a different UL-DLconfiguration.

The method 1000 can further comprise adapting a UL-DL configuration insubstantially real-time to changing uplink and downlink traffic demandsat any of the first eNodeB and the adjacent eNodeB. The adapted UL-DLconfiguration can pertain to the common UL-DL configuration where thefirst determination, discussed above, has been made. The changing uplinkand downlink traffic demands can be communicated between eNodeBs in thecommon cluster over a low-latency backhaul infrastructure.Alternatively, the adapted UL-DL configuration can pertain to the hefirst TDD configuration where the second determination, discussed above,has been made.

The method 1000 can also further comprise communicating at least one ofUL and DL traffic needs between the first eNodeB and the adjacent eNodeBin the common cluster over a low-latency backhaul infrastructure. Insome embodiments, the method can further comprise determining at leastone of the common UL-DL configuration and a restricted set of UL-DLconfigurations for the common UL-DL configuration. This determinationcan be made on the basis of at least one of joint UL and DL needsthroughout the common cluster. The determination can also be made bysplitting a difference between UL and DL traffic demands at the firsteNodeB and the adjacent eNodeB in the common cluster.

FIG. 11 illustrates a device 1102 operating at an illuminated/firsteNodeB 1104 that is illuminated by a DL transmission 1106 from atransmit/adjacent eNodeB 1108. In alternative embodiments, the devicecan reside at a network level, such as within the Evolved Packet Core(EPC) or via an external network connected to the EPC via a Packet DataNetwork Gateway (PDN-GW). The device, for adapting to asymmetric UL andDL traffic loads in a WWAN in accordance with another example, caninclude various modules. Such modules can include a coupling measurementmodule 1110, an analysis module 1120, a configuration module 1130, and acommunication module 1140.

The coupling measurement module 1110 can be configured to make acoupling measurement on a DL transmission from an adjacent eNodeB to thefirst eNodeB. The analysis module 1120 can be in communication with thecoupling measurement module. Additionally, the analysis module can beconfigured to compare the coupling measurement to a coupling threshold.Where the coupling measurement is at or above the coupling threshold,the analysis module determines that the first eNodeB and the adjacenteNodeB are coupled. Where the coupling measurement is below the couplingthreshold, the analysis module determines that the first eNodeB and theadjacent eNodeB are isolated.

The configuration module 1130 can be in communication with the analysismodule 1120. Additionally, the configuration module can be configured toidentify a common UL-DL configuration where the first eNodeB and theadjacent eNodeB are coupled. The configuration module can also identifya first UL-DL configuration for the first eNodeB independently of asecond UL-DL configuration for the adjacent eNodeB where the firsteNodeB and the adjacent eNodeB are isolated.

In some embodiments, the device 1102 can also include a communicationmodule 1140, in communication with the configuration module 1130. Thecommunication module can be configured to send traffic directioninformation about traffic direction needs at the first eNodeB to theadjacent eNodeB. It can also be configured to receive traffic directioninformation about traffic direction needs at the adjacent eNodeB.

In certain embodiments, an update module 1132 can be provided incommunication with the configuration module 1130. Where the first eNodeBand the adjacent eNodeB are coupled in the common cluster, the updatemodule can be configured to update the common UL-DL configuration toadapt in substantially real time to changing traffic direction needs atboth the first eNodeB and the adjacent eNodeB. Where the first eNodeBand the adjacent eNodeB are isolated, the update module can update thefirst TDD configuration independently of the second TDD configuration toadapt in real time to changing traffic direction needs at the firsteNodeB.

In such embodiments, a calculation module 1122, in communication withthe analysis module 1120, can also be provided. The calculation modulecan be configured to calculate the coupling threshold. This calculationcan be performed on the basis of estimating a level of DL inter-cellinterference by analyzing a coupling metric in terms of the couplingmeasurement and a transmission power of the adjacent eNodeB. Thecalculation can also be performed on the basis of useful signal powersassociated with multiple user terminals associated with the firsteNodeB. Additionally, among other approaches, the calculation may bemade on the basis of UL inter-cell interference associated with multipledeployed eNodeBs during a time where all eNodeBs operate to receiveuplink transmission.

Additionally, some embodiments can include an optimization module 1124in communication with the calculation module 1122. The optimizationmodule can be configured to optimize the coupling threshold.Optimization within the optimization module can be based on feedback.Feedback can provide information about throughput, a path gainmeasurement, SINR, system traffic loading, and/or cell traffic loadinginformation, among other possibilities.

Some embodiments can include a merger module 1142 in communication withthe communication module 1140. The merger module can be configured torespond to an eNodeB list from a second cluster of coupled eNodeBs. Thelist can be used to determine a need to merge the second cluster and afirst cluster to which the eNodeB belongs. With respect to such adetermination, the first cluster can be any of the common cluster andthe first eNodeB in isolation. Such a determination is made where theeNodeB list includes an intersection eNodeB common to the first clusterand the second cluster. Otherwise, the merger module makes adetermination to leave the first cluster unaltered.

Also, an isolation module 1144, in communication with the communicationmodule 1140, can be included is some embodiments. The isolation module1144 can be configured to indicate when a second cluster and an isolatedeNodeB belonging to the common cluster can have a UL-DL configurationdistinct from the common UL-DL configuration of the common cluster. Theability to have different UL-DL configurations can be due to changingtransmission patterns.

FIG. 12 depicts a flowchart for a particular clustering method 1200 formitigating interference during adaption to asymmetric downlinktransmission among multiple eNodeBs, in accordance with an example. Themethod can, but need not necessarily, be embedded in a computer programproduct comprising a non-transitory computer usable medium. The computerreadable medium can have a computer readable program code embodiedtherein. The computer readable program code can be adapted to beexecuted to implement instructions for the method. In embodimentsembedded in a computer program product, the computer program product canreside on one or more of an MCN, an LPN, and a network level entity.

The method 1200 can comprise determining 1210 a coupling level between afirst eNodeB and each of at least one additional eNodeB. The method canproceed by clustering 1220 the first eNodeB with any eNodeB from the atleast one additional eNodeB with a corresponding coupling level greaterthan a coupling threshold. The clustering can create a common cluster.The common cluster can include one of only the first eNodeB, the firsteNodeB and one additional eNodeB, and the first eNodeB and multipleadditional eNodeBs. An additional step can involve setting 1230 a commonTDD configuration for the common cluster.

In embodiments where the common cluster comprises at least oneadditional eNodeB in addition to the first eNodeB, such embodiments canfurther comprise communicating directional traffic information from thefirst eNodeB to the at least one additional eNodeB in the common clusterover a backhaul link. Such embodiments can also further comprisereceiving at the first eNodeB directional traffic information over thebackhaul link from the at least one additional eNodeB in the commoncluster. Such embodiments can also further comprise monitoring thecommon cluster for changing directional traffic demands in the commoncluster. Additionally, they can comprise adapting the common TDDconfiguration for the common cluster in substantially real time. Theseadaptations can respond to the changing directional traffic demandsindependently of any TDD configuration corresponding to any eNodeBoutside of the common cluster.

The coupling threshold can be calculated by using knowledge about atleast one transmission power of at least one of the at least oneadditional eNodeBs to estimate a level of inter-cell interference. Incertain embodiments, the coupling threshold may be calculated byaveraging a plurality of useful signal powers associated with multipleeNodeBs in the common cluster. Also, the coupling threshold can becalculated by averaging a plurality of levels of UL inter-cellinterference associated with multiple eNodeBs in the common cluster.These levels of uplink inter-cell interference can be measured during atime where all eNodeBs in the common cluster operate to receive uplinktransmission. Additional approaches to calculating the couplingthreshold, apparent to those of ordinary skill in the art, are possible.Also, some embodiments can further comprise optimizing the couplingthreshold with feedback about one or both of throughput received at theat least one additional eNodeB and a coupling level for the at least oneadditional eNodeB.

The method 1200 can also further comprise acquiring a list of eNodeBs ina second cluster of eNodeBs from a contact eNodeB in the second clusterof eNodeBs. The second cluster of eNodeBs can have any number of membereNodeBs, including a single member eNodeB. Where the common cluster andthe second cluster share an intersection eNodeB, such embodiments canfurther comprise merging the second cluster of eNodeBs with the commoncluster for purposes of determining the common TDD configuration.

FIG. 13 illustrates a device 1300 for avoiding interference whileadapting to asynchronous directional traffic at various eNodeBs in aWWAN in accordance with another example. The device can operate at aneNodeB and/or at a network level. Within the device, several modules canbe included, such as an interference module 1310, an isolation module1320, and a traffic response module 1330. The device can reside on oneor more of an MCN eNodeB, an LPN, and a network entity at a networklevel.

The interference module 1310 can be configured to estimate aninterference level from a DL eNodeB as received at the first eNodeB. Theisolation module 1320, in communication with the interference module,can be configured to indicate where the interference level issufficiently low to allow the first eNodeB to be isolated. An isolatedfirst eNodeB can accommodate UL transmission while the downlink eNodeBtransmits a downlink transmission. Where the interference level issufficiently high, the isolation module can require the first eNodeB andthe downlink eNodeB to be aggregated in a common cluster to synchronizeor coordinate transmission directions. The traffic response module 1330,in communication with the isolation module, can be configured to createa TDD configuration. Where the first eNodeB belongs to the commoncluster, the TDD configuration can respond to directional traffic foreNodeBs associated with the first eNodeB in the common cluster. Wherethe first eNodeB is isolated, the TDD configuration can independentlyrespond to directional traffic for the first eNodeB.

A monitoring module 1332 can also be included in the device 1300 incommunication with the traffic response module 1330. The monitoringmodule can be configured to monitor directional traffic for eNodeBsassociated with the first eNodeB in the common cluster where the firsteNodeB belongs to the common cluster. In such embodiments, directionaltraffic information can be communicated from at least one other eNodeBin the common cluster to the first eNodeB over a low-latency backhaulinfrastructure. Where the first eNodeB is isolated, the monitoringmodule can monitor just the first eNodeB. The monitoring module can alsoindicate to the traffic response module when to change the TDDconfiguration to accommodate a change in directional traffic insubstantially real time.

The device 1300 can also include a merger module 1334, in communicationwith the traffic response module 1330. The merger module 1334 can beconfigured to include at least one of an additional eNodeB and anadditional cluster to the common cluster. This addition can be made upona determination that at least one of the additional eNodeB and theadditional cluster share a common eNodeB with the common cluster.Additionally, the device can include a balancing module, incommunication with the traffic response module. The balance module canbe configured to reconcile competing uplink and downlink directionaltraffic demands at different eNodeBs within the common cluster to createthe TDD configuration. The TDD configuration can be created so as torespond to the competing traffic demands.

Some embodiments can include an optimization module 1322 incommunication with the isolation module 1320. The isolation module canbe configured to optimize a coupling threshold used to determine whetherthe first eNodeB belongs to the common cluster by monitoring theinter-cell interference level from opposite transmission directions ofadjacent cells. The optimization module can also optimize the couplingthreshold by analyzing traffic adaptation capabilities and trafficdemands within a set of isolated cells and a set of common cell clusters

FIG. 14 provides an example illustration of a mobile device, such as UE,a mobile station (MS), a mobile wireless device, a mobile communicationdevice, a tablet, a handset, or other type of mobile wireless device.The mobile device can include one or more antennas configured tocommunicate with a base station (BS), an eNodeB, or other type of WWANaccess point. While two antennas are shown, the mobile device may havebetween one and four or more antennas. The mobile device can beconfigured to communicate using at least one wireless communicationstandard including 3GPP LTE, Worldwide interoperability for MicrowaveAccess (WiMAX), High Speed Packet Access (HSPA), Bluetooth, WiFi, orother wireless standards. The mobile device can communicate usingseparate antennas for each wireless communication standard or sharedantennas for multiple wireless communication standards. The mobiledevice can communicate in a wireless local area network (WLAN), awireless personal area network (WPAN), and/or a WWAN.

FIG. 14 also provides an illustration of a microphone and one or morespeakers that can be used for audio input and output from the mobiledevice. The display screen may be a liquid crystal display (LCD) screen,or other type of display screen such as an organic light emitting diode(OLED) display. The display screen can be configured as a touch screen.The touch screen may use capacitive, resistive, or another type of touchscreen technology. An application processor and a graphics processor canbe coupled to internal memory to provide processing and displaycapabilities. A non-volatile memory port can also be used to providedata input/output options to a user. The non-volatile memory port mayalso be used to expand the memory capabilities of the mobile device. Akeyboard may be integrated with the mobile device or wirelesslyconnected to the mobile device to provide additional user input. Avirtual keyboard may also be provided using the touch screen.

It should be understood that many of the functional units described inthis specification have been labeled as modules, in order to moreparticularly emphasize their implementation independence. For example, amodule may be implemented as a hardware circuit comprising custom VLSIcircuits or gate arrays, off-the-shelf semiconductors such as logicchips, transistors, or other discrete components. A module may also beimplemented in programmable hardware devices such as field programmablegate arrays, programmable array logic, programmable logic devices or thelike.

Modules may also be implemented in software for execution by varioustypes of processors. An identified module of executable code may, forinstance, comprise one or more physical or logical blocks of computerinstructions, which may, for instance, be organized as an object,procedure, or function. Nevertheless, the executables of an identifiedmodule need not be physically located together, but may comprisedisparate instructions stored in different locations which, when joinedlogically together, comprise the module and achieve the stated purposefor the module.

Indeed, a module of executable code may be a single instruction, or manyinstructions, and may even be distributed over several different codesegments, among different programs, and across several memory devices.Similarly, operational data may be identified and illustrated hereinwithin modules, and may be embodied in any suitable form and organizedwithin any suitable type of data structure. The operational data may becollected as a single data set, or may be distributed over differentlocations including over different storage devices, and may exist, atleast partially, merely as electronic signals on a system or network.The modules may be passive or active, including agents operable toperform desired functions.

Various techniques, or certain aspects or portions thereof, may take theform of program code (i.e., instructions) embodied in tangible media,such as floppy diskettes, CD-ROMs, hard drives, or any othermachine-readable storage medium wherein, when the program code is loadedinto and executed by a machine, such as a computer, the machine becomesan apparatus for practicing the various techniques. In the case ofprogram code execution on programmable computers, the computing devicemay include a processor, a storage medium readable by the processor(including volatile and non-volatile memory and/or storage elements), atleast one input device, and at least one output device. One or moreprograms that may implement or utilize the various techniques describedherein may use an application programming interface (API), reusablecontrols, and the like. Such programs may be implemented in a high levelprocedural or object oriented programming language to communicate with acomputer system. However, the program(s) may be implemented in assemblyor machine language, if desired. In any case, the language may be acompiled or interpreted language, and combined with hardwareimplementations.

Reference throughout this specification to “one embodiment” or “anembodiment” means that a particular feature, structure, orcharacteristic described in connection with the embodiment is includedin at least one embodiment of the present invention. Thus, appearancesof the phrases “in one embodiment” or “in an embodiment” in variousplaces throughout this specification are not necessarily all referringto the same embodiment.

As used herein, a plurality of items, structural elements, compositionalelements, and/or materials may be presented in a common list forconvenience. However, these lists should be construed as though eachmember of the list is individually identified as a separate and uniquemember. Thus, no individual member of such list should be construed as ade facto equivalent of any other member of the same list solely based ontheir presentation in a common group without indications to thecontrary. In addition, various embodiments and example of the presentinvention may be referred to herein along with alternatives for thevarious components thereof. It is understood that such embodiments,examples, and alternatives are not to be construed as defactoequivalents of one another, but are to be considered as separate andautonomous representations of the present invention.

Furthermore, the described features, structures, or characteristics maybe combined in any suitable manner in one or more embodiments. In thefollowing description, numerous specific details are provided, such asexamples of materials, fasteners, sizes, lengths, widths, shapes, etc.,to provide a thorough understanding of embodiments of the invention. Oneskilled in the relevant art will recognize, however, that the inventioncan be practiced without one or more of the specific details, or withother methods, components, materials, etc. In other instances,well-known structures, materials, or operations are not shown ordescribed in detail to avoid obscuring aspects of the invention.

While the forgoing examples are illustrative of the principles of thepresent invention in one or more particular applications, it will beapparent to those of ordinary skill in the art that numerousmodifications in form, usage and details of implementation can be madewithout the exercise of inventive faculty, and without departing fromthe principles and concepts of the invention. Accordingly, it is notintended that the invention be limited, except as by the claims setforth below.

What is claimed is:
 1. A method for interference management and trafficadaptation in a wireless network with different Up Link and Down Linktime slots and adaptive, asynchronous directional traffic resourceallocation comprising: measuring, at a first eNodeB, a unit of couplinginformation between the first eNodeB and an adjacent eNodeB; making aclustering determination based on the unit of coupling information,wherein the clustering determination comprises one of a firstdetermination that the first eNodeB and the adjacent eNodeB belong in acommon cluster and a second determination that the first eNodeB and theadjacent eNodeB are isolated; and configuring the first eNodeB and theadjacent eNodeB with a common Up Link-Down Link (UL-DL) configurationwhere the first determination has been made and configuring the firsteNodeB with a first UL-DL configuration independently from a potentiallydiffering UL-DL configuration pertaining to the adjacent eNodeB wherethe second determination has been made.
 2. The method of claim 1,wherein making the clustering determination based on the unit ofcoupling information further comprises reaching the first determinationwhere at least one of a first condition and a second condition is met,wherein: the first condition is that a performance of the first eNodeBis not substantially degraded by a transmission direction of theadjacent eNodeB, and the second condition is that a change of thetransmission direction of the adjacent eNodeB does not substantiallydegrade the performance of the first eNodeB; and, otherwise reaching thesecond determination.
 3. The method of claim 2, wherein a couplingmetric is selected to characterize the unit of coupling information anda coupling threshold is used to determine that the performance of thefirst eNodeB is substantially degraded where the unit of couplinginformation is one of at the coupling threshold and above the couplingthreshold for the coupling metric, otherwise that the first eNodeB isnot substantially degraded where the unit of coupling information isbelow the coupling threshold for the coupling metric.
 4. The method ofclaim 3, further comprising determining the coupling threshold based onone of: an estimate of a level of inter-cell interference calculatedfrom the unit of coupling information where a transmission power of theadjacent eNodeB is known; an average power of a useful UL signal; and anaverage level of uplink inter-cell interference where all eNodeBs in thecommon cluster operate to receive uplink transmission.
 5. The method ofclaim 2, further comprising one of: merging the common cluster with asecond cluster where the common cluster and the second cluster have atleast one eNodeB in common that couples the common and adjacentclusters; and dividing a merged cluster into sub-clusters where at leastone adapted eNodeB within the merged cluster can adapt to changingtraffic demands in a manner such that at least one of the firstcondition and the second condition no longer obtain between the at leastone adapted eNodeB and at least one additional eNodeB in the mergedcluster, such that each sub-cluster can apply a different UL-DLconfiguration.
 6. The method of claim 1, further comprising adapting aUL-DL configuration in substantially real-time to changing uplink anddownlink traffic demands at any of the first eNodeB and the adjacenteNodeB, wherein the UL-DL configuration comprises one of: the commonUL-DL configuration where the first determination has been made and thechanging UL and DL traffic demands are communicated between eNodeBs inthe common cluster over a low-latency backhaul infrastructure, and thefirst UL-DL configuration where the second determination has been made.7. The method of claim 1, further comprising communicating at least oneof uplink and downlink traffic needs between the first eNodeB and theadjacent eNodeB in the common cluster over a low-latency backhaulinfrastructure.
 8. The method of claim 7, further comprising determiningat least one of the common UL-DL configuration and a restricted set ofUL-DL configurations for the common UL-DL configuration on the basis ofat least one of joint UL and DL needs throughout the common cluster andsplitting a difference between UL and DL traffic demands at the firsteNodeB and the adjacent eNodeB in the common cluster.
 9. A device foradapting to asymmetric uplink and Down Link traffic loads in a wirelessnetwork comprising: a coupling measurement module, operating at one of afirst eNodeB and a network level entity, configured to a make couplingmeasurement on a Down Link (DL) transmission from an adjacent eNodeB tothe first eNodeB; an analysis module, in communication with the couplingmeasurement module, configured to compare the coupling measurement to acoupling threshold to determine that the first eNodeB and the adjacenteNodeB are coupled where the coupling measurement is one of at thecoupling threshold and above the coupling threshold, and to determinethat the first eNodeB and the adjacent eNodeB are isolated where thecoupling measurement is below the coupling threshold; and aconfiguration module, in communication with the analysis module,configured to identify a common Up Link (UL)-DL configuration where thefirst eNodeB and the adjacent eNodeB are coupled and a first UL-DLconfiguration for the first eNodeB independently of a second UL-DLconfiguration for the adjacent eNodeB where the first eNodeB and theadjacent eNodeB are isolated.
 10. The device of claim 9, furthercomprising a communication module, in communication with theconfiguration module, configured to do at least one of send trafficdirection information about traffic direction needs at the first eNodeBto the adjacent eNodeB; and receive traffic direction information abouttraffic direction needs at the adjacent eNodeB.
 11. The device of claim9, further comprising an update module, in communication with theconfiguration module, configured to do one of: update the common UL-DLconfiguration to adapt in substantially real time to changing trafficdirection needs at both the first eNodeB and the adjacent eNodeB wherethe first eNodeB and the adjacent eNodeB are coupled in the commoncluster; and update the first UL-DL configuration independently of thesecond UL-DL configuration to adapt substantially in real time tochanging traffic direction needs at the first eNodeB where the firsteNodeB and the adjacent eNodeB are isolated.
 12. The device of claim 11,further comprising a calculation module, in communication with theanalysis module, configured to calculate the coupling threshold based onat least one of: an estimate of a level of DL inter-cell interference byanalyzing a coupling metric in terms of the coupling measurement andtransmission power of the adjacent eNodeB; useful signal powersassociated with multiple user terminals associated with the firsteNodeB; and uplink inter-cell interference associated with multipledeployed eNodeBs measured during a time where all eNodeBs operate toreceive a UL transmission.
 13. The device of claim 12, furthercomprising an optimization module, in communication with the calculationmodule, configured to optimize the coupling threshold based on feedbackabout at least one of throughput, a coupling measurement, Signal toInterference plus Noise Ratio (SINR), and one of system and cell trafficloading information can be used to optimize the value of couplingthreshold.
 14. The device of claim 11, further comprising a mergermodule, in communication with the communication module, configured torespond to an eNodeB list from a second cluster of coupled eNodeBs todetermine a need to merge the second cluster and a first cluster towhich the eNodeB belongs, wherein the first cluster can be any of thecommon cluster and the first eNodeB in isolation, where the eNodeB listincludes an intersection eNodeB common to the first cluster and thesecond cluster; and otherwise to leave the first cluster unaltered. 15.The device of claim 11, further comprising an isolation module, incommunication with the communication module, configured to indicate whenat least one of the second cluster and an isolated eNodeB belonging tothe common cluster can have a UL-DL configuration distinct from thecommon UL-DL configuration of the common cluster.
 16. A computer programproduct comprising a non-transitory computer usable medium having acomputer readable program code embodied therein, the computer readableprogram code adapted to be executed to implement instructions for amethod for mitigating interference during adaption to asymmetric DLtransmission among multiple eNodeBs, comprising: determining a couplinglevel between a first eNodeB and each of at least one additional eNodeB;clustering the first eNodeB with any eNodeB from the at least oneadditional eNodeB with a corresponding coupling level greater than acoupling threshold to create a common cluster, wherein the commoncluster can include one of only the first eNodeB, the first eNodeB andone additional eNodeB, and the first eNodeB and multiple additionaleNodeBs; and, setting a common Time Division Duplex (TDD) configurationfor the common cluster.
 17. The computer program product of claim 16,further comprising, where the common cluster comprises the at least oneadditional eNodeB in addition to the first eNodeB, at least one of:communicating directional traffic information from the first eNodeB tothe at least one additional eNodeB in the common cluster over a backhaullink; and receiving at the first eNodeB directional traffic informationover the backhaul link from the at least one additional eNodeB in thecommon cluster.
 18. The computer program product of claim 17, furthercomprising: monitoring the common cluster for changing directionaltraffic demands in the common cluster; and adapting the common TDDconfiguration for the common cluster in substantially real time torespond to the changing directional traffic demands independently of anyTDD configuration corresponding to any eNodeB outside of the commoncluster.
 19. The computer program product of claim 16, furthercomprising calculating the coupling threshold by: using knowledge aboutat least one transmission power of at least one of the at least oneadditional eNodeBs to estimate a level of inter-cell interference;averaging a plurality of useful signal powers associated with multipleeNodeBs in the common cluster; and averaging a plurality of levels of ULinter-cell interference associated with multiple eNodeBs in the commoncluster measured during a time where all eNodeBs in the common clusteroperate to receive UL transmission.
 20. The computer program product ofclaim 16, further comprising optimizing the coupling threshold withfeedback about at least one of throughput received at the at least oneadditional eNodeB and a coupling level for the at least one additionaleNodeB.